The use of engineered I-beams in western style construction has become common place particularly for use as a component in floors, joists and beams, as they are both lighter and less prone to warping than solid wood joists. Conventional wood based I-beams typically are constructed from an oriented strand board or fiberboard web bound by top and bottom flange sections also typically constructed of high quality fir or laminated veneer lumber. I-beams are capable of supporting higher loads than an equivalent sized dimensional lumber beam and are therefore an economic means of construction. In a typical application the I-beams are intended to span a distance wherein the ends of the I-beam are supported and a load is applied along the length of the beam. In this configuration, the top flange is longitudinally in compression whilst the bottom flange is in tension. The web material maintains the distance between the top and bottom flanges and is in shear when the beam is under load, very much like the cross members in a truss. Because the load is largely borne by the top and bottom flanges, the flanges must be of high quality material. Ideally the flanges should be constructed from a single continuous piece of lumber or an engineered laminated veneer lumber; however, in practice seams are required to achieve length. Consequently seams must also be designed to bear the required loads.
I-beams constructed of wood have a number of advantages; however, there has been some concern as to their rapid loss of strength in a fire if unprotected. Also, wood as a construction material is general becoming a scarcer commodity, thus increasingly expensive, and the harvesting of wood is coming under increased environmental scrutiny. Various alternate renewable materials have been proposed to replace wood in engineered I-beams; however, ideally one would prefer the use of renewable and sustainable materials that impose a low environmental impact to harvest and process. Bamboo is such a material.
Bamboo is a prolific woody grass that has long been used in various forms as a construction material. Bamboo possesses numerous properties advantageous to the construction industry. Of particular utility is the high compression and tensile strength when used in pole form, also referred to as bamboo cane, as a support member or load bearing element in a structure. However use of bamboo in traditional western construction practices has been problematic as the tubular bamboo culm must be processed into a construction material having western style standardized dimensions, durability and strength characteristics. These difficulties are particularly pronounced as demonstrated by prior art attempts to utilize bamboo in I-beam structures wherein the bamboo is typically shredded, chipped, stranded, flaked and reconstituted into an oriented strand board; or, ripped and milled longitudinally along the culm into solid small narrow strips assembled into stacks and bonded into board form.
Use of bamboo culm in an I-beam component, without compromising the beneficial characteristics of a tubular cane, provides numerous advantages over wood including higher overall strength for the same volume of material content, higher fire resistance, lower weight, and high durability and flexibility.
Bamboo is generally lower cost than wood. Bamboo is fast growing requiring only three to four years before harvesting an individual timber grade bamboo culm, a growth time significantly less than wood. As compared to wood, bamboo has a higher rot resistance and resistance to insect infestation than most woods. Further, bamboo has a higher level of carbon sequestration than most woods. Therefore, what is needed is an I-beam construction component principally utilizing bamboo while maintaining the bamboo culm beneficial structural characteristics largely in tact thereby capitalizing on the advantageous characteristics of bamboo timber while providing a material with substantially consistent and predictable dimensions and structural characteristics such as timber or other load bearing structural components.